The present invention relates to a device for transferring products from a feeder conveyor belt to a discharge conveyor belt, comprising a linear motor with conveyor elements, which are guided displaceably on a guide and have grippers for temporarily picking up products. A method for operating the device also lies within the scope of the invention.
Conventional belt systems are generally used for supplying products, for example chocolate bars which have already been packaged, to a tube packaging machine to produce a multipack. Said belt systems take over the products from the outlet belt of a tube packaging machine, rotate said products, form a short product jam to buffer small fluctuations in the speed, accelerate the products to the speed of the subsequent packaging machine and finally synchronize said products with the feed chain of said machine. A similar problem exists when delivering products from a product array in order to supply said products individually to a tube packaging machine. In this case too, the products are removed from the product array by means of a delivery station, which consists especially of a belt system provided with a switch, and are then aligned, backed up, separated and accelerated by means of a plurality of belts, and synchronized with the packaging machine and passed to the feed chain of the packaging machine. Said systems consist of a multiplicity of belts and thus rapidly reach a length of up to 10 m.
The above problems can be solved more compactly by using a feed system consisting of circulating, individual linear motor carriages which grip the products and deposit them directly into the feed chain. In this case, the products can be rotated during the transport path, and synchronization can take place directly by specific acceleration or braking of the individual products in their carriages. Systems of this type are known, for example from U.S. Pat. No. 7,134,258 and EP-A-1 123 886.
Disadvantages of this system include the large outlay associated with the circulating linear motor carriages. The feeding of vacuum for gripping the products to a circulating system is demanding, and a large and expensive linear motor section is required for the forward movement and return movement and the two deflections. Also, the carriages which are in circulation at a particular instant are not available, this increasing the number of carriages required and additionally increasing the cost of the system. Furthermore, the deflecting sections are realized only by means of additional technical outlay, since the narrow motor gap required on the deflecting sections between the fixed primary part and moving secondary part of the carriages cannot be ensured. In addition, the circulation requires a comparatively large radius, which makes the entire system have a large overall volume.
Furthermore, products can also be placed into the feed chain of a packaging machine by means of a pick and place robot. The disadvantages here include the fact that a vision system, with which the robot can identify the products, is generally required, and the low capacity of approximately 100 products/minute which can be achieved by a robot. In general, however, capacities of 400-800 products/minute are sought, which requires a large number of robots and therefore causes high costs and requires a large amount of space.
Groups may also be formed by means of a grouping device, such as a “dancer chain” and transferred by means of a two-axle robot with a multipicker—a “top loader”. The space required and the technical outlay are also large here and the flexibility is restricted.